1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
/// Folds a flat list into a tree.
final class TreeFolder {
private enum NestableKind { case unordered, ordered, quote }
private let blocks: [NorgBlock]
private var index = 0
private var strongReset = false
init(_ blocks: [NorgBlock]) {
self.blocks = blocks
}
func fold() -> [NorgNode] {
foldStructural(level: 0)
}
/// Folds structural items, that can have any block under them.
private func foldStructural(level: Int) -> [NorgNode] {
var nodes: [NorgNode] = []
while index < blocks.count {
let block = blocks[index]
switch block {
case .heading(let headingLevel, _, _, _):
// A heading of the same or higher level belongs to an ancestor;
// leave it for the caller.
if headingLevel <= level { return nodes }
index += 1
let children = foldStructural(level: headingLevel)
nodes.append(NorgNode(block: block, children: children))
if strongReset {
if level == 0 { strongReset = false } else { return nodes }
}
case .unorderedListItem(let itemLevel, _, _, _):
nodes.append(foldNestableItem(block, kind: .unordered, level: itemLevel))
case .orderedListItem(let itemLevel, _, _, _):
nodes.append(foldNestableItem(block, kind: .ordered, level: itemLevel))
case .quote(let itemLevel, _, _, _):
nodes.append(foldNestableItem(block, kind: .quote, level: itemLevel))
case .weakDelimiter:
index += 1
if level > 0 { return nodes }
case .strongDelimiter:
index += 1
if level > 0 {
strongReset = true
return nodes
}
default:
index += 1
nodes.append(NorgNode(block: block, children: []))
}
}
return nodes
}
/// Folds nestable items that can only consume more of their kind.
private func foldNestableItem(_ block: NorgBlock, kind: NestableKind, level: Int) -> NorgNode {
index += 1
var children: [NorgNode] = []
while index < blocks.count, let child = nestableDescriptor(blocks[index]),
child.kind == kind, child.level > level {
children.append(foldNestableItem(blocks[index], kind: child.kind, level: child.level))
}
return NorgNode(block: block, children: children)
}
/// The kind and nesting level of a nestable block, or `nil` if `block` is not
/// a nestable item.
private func nestableDescriptor(_ block: NorgBlock) -> (kind: NestableKind, level: Int)? {
switch block {
case .unorderedListItem(let level, _, _, _): return (.unordered, level)
case .orderedListItem(let level, _, _, _): return (.ordered, level)
case .quote(let level, _, _, _): return (.quote, level)
default: return nil
}
}
}
|
